Tunable molecular dipole moments and orientations for efficient and stable perovskite solar cells

Molecules with positive and negative ends, known as dipolar molecules, are effective tools for the interfacial modifications of perovskites. However, the impact of their dipole moments, the system’s overall polarity, and their orientations remains unexplored. In this work, we designed four molecules with different electron-donating/withdrawing groups, resulting in varying dipole moments and orientations, and analyzed their impact on performance when applied to perovskite films as surface modifiers. The perovskite treated with (4-(trifluoromethyl)phenyl)methanaminium iodide (PMA-CF₃), which has the largest dipole moment and ordered parallel orientation, exhibited the most matched energy level with C₆₀, which facilitated the electron transport and hindered the hole transport at the interface. The champion devices treated with PMA-CF₃ exhibited the best performance with a power conversion efficiency of 26.04% (a certified steady-state efficiency of 25.62% for 350s maximum power point tracking) and excellent storage and light soaking stability.